diff --git a/CHANGELOG b/CHANGELOG
index b2cb4cdcf..84d4f9ae5 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -7,6 +7,7 @@ CHANGELOG Roundcube Webmail
 - Fix PHP fatal error when visiting Vacation interface and there's no sieve script yet
 - Fix setting max packet size for DB caches and check packet size also in shared cache
 - Fix needless security warning on BMP attachments display (#1490282)
+- Fix handling of some improper constructs in format=flowed text as per the RFC3676[4.5] (#1490284)
 
 RELEASE 1.1.0
 -------------
diff --git a/program/lib/Roundcube/rcube_mime.php b/program/lib/Roundcube/rcube_mime.php
index 3f2fcc330..e9cab6107 100644
--- a/program/lib/Roundcube/rcube_mime.php
+++ b/program/lib/Roundcube/rcube_mime.php
@@ -520,7 +520,7 @@ class rcube_mime
                     // remove space-stuffing
                     $line = preg_replace('/^ /', '', $line);
 
-                    if (isset($text[$last]) && $line
+                    if (isset($text[$last]) && $line && !$q_level
                         && $text[$last] != '-- '
                         && $text[$last][strlen($text[$last])-1] == ' '
                     ) {
diff --git a/tests/Framework/Mime.php b/tests/Framework/Mime.php
index 43773f1a5..4cf84cbb0 100644
--- a/tests/Framework/Mime.php
+++ b/tests/Framework/Mime.php
@@ -155,6 +155,21 @@ class Framework_Mime extends PHPUnit_Framework_TestCase
         $this->assertEquals($unfolded, rcube_mime::unfold_flowed($flowed), "Test correct unfolding of quoted lines");
     }
 
+    /**
+     * Test format=flowed unfolding (#1490284)
+     */
+    function test_unfold_flowed2()
+    {
+        $flowed   = "> culpa qui officia deserunt mollit anim id est laborum.\r\n"
+                    ."> \r\n"
+                    ."Sed ut perspiciatis unde omnis iste natus error \r\nsit voluptatem";
+        $unfolded = "> culpa qui officia deserunt mollit anim id est laborum.\r\n"
+                    ."> \r\n"
+                    ."Sed ut perspiciatis unde omnis iste natus error sit voluptatem";
+
+        $this->assertEquals($unfolded, rcube_mime::unfold_flowed($flowed), "Test correct unfolding of quoted lines [2]");
+    }
+
     /**
      * Test wordwrap()
      */